Bennett said his experience with Arizona elections in this and prior years convinces him more transparency in funding sources is needed. He said existing state laws focus largely on contribution limits for candidate races, which may not be the best thing for voter education. "We need to think more about how to more immediately provide disclosure as to who's giving and not focus so much on how much they gave," Bennett said.

"As we've found out, if you give to one group and they give to another group, those monies can kind of be accumulated," he said. "And it's not until well after the election that you know who was really behind the first giving," if then.

Under Arizona law, no formal reporting is required, even after the election. And on ballot measures, unlike candidate campaigns, there is no limit on how much any individual, business or organization can give.